Control of a particular coarse-fine micro-positioning system based on a magnetic actuation

The device whose control is presented here allows to push micro-objects located in a drop of water between two glass panes. The distance between both glass panes is a few hundred micrometers. Objects are pushed with a small ferromagnetic particle whose size is 100 × 100 × 20 μm³, and which is moved thanks to a permanent magnet. The authors previously (2002) presented the dynamic behavior of this micromanipulation device. We present here an original control strategy which use the manipulator orientation to achieve a good precision despite the "stick slip effect". The position precision obtained is 1 μm and is limited by the camera resolution.